Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
(i) Li
(ii) Na
(iii) K
(iv) Cs
The answer is the option (i) Li has an extremely high hydrogen enthalpy. So, its reaction with water releases a high amount of energy, most of which is consumed in fusion, vaporization and ionization. Hence, its reaction with water is less vigorous.